Calcium chloride is a widely used industrial chemical. Significant volumes are used as a curing accelerator in concrete, as an additive in drilling muds to control density and clay flocculation, as a drainage aid in paper mills, as a dessicant in refrigeration plants, and as a heat transfer fluid in closed recirculating cooling systems operating at temperatures below zero degrees C.
Calcium chloride brines in applications such as for concrete accelerators or as additives to drilling muds create serious corrosion problems. Most construction concrete is reinforced with steel bars which are embedded in the concrete and the presence of calcium chloride in the concrete accelerates corrosive attack of the reinforcing steel. The calcium chloride in drilling muds causes an accelerated corrosion of well tubing and equipment used in oil drilling applications. The use of calcium chloride as a drainage aid in the paper industry has been limited by the corrosive nature of its solutions.
In closed recirculating cooling systems where calcium chloride brine is employed as a heat transfer medium, corrosion control is necessary. Historically, chromates have been used to inhibit corrosion in calcium chloride brine systems. Chromates are soluble in these concentrated solutions and are extremely efficacious in these aggressive environments. However, the environmental and health concerns that the use of chromates presents have resulted in their being phased out as corrosion inhibitors. Nitrites are also soluble and compatible in calcium chloride brines and have been employed as a replacement for chromates. However, high levels of nitrite, that is up to 0.5%, are necessary for corrosion protection in calcium chloride brine systems.